The present invention relates to an improved audio alarm system capable of use in combination with a clock-radio for awakening the user at a preselected time.
Audio alarm systems of the general type herein are known and have been in use for some time, both in the United States and elsewhere. These systems are employed with a clock radio having capability of being set for automatic wake-up at which time a mechanism of the clock causes a switch, or the equivalent, to close thereby to close the circuit to the radio. The radio then commences operation. Usually such clock-radios have capability of providing, also, after a period of time during which the radio alone shall play the sounding of a buzzer-type device, which is conventionally activated and which continues until terminated by the user. Both the buzzer and the radio provide their alarm continuously at the same level of volume until they are one of the same, preferably the buzzer, controlled manually to an "off" condition.
The prior art also includes forms of electronic alarm clocks as represented by U.S. Pat. No. 3,681,916 to Itoyama et al. This particular device provides an alarm of continuous oscillatory or intermittent oscillatory sound which appears and disappears at a regular cycle. The sound, further, is capable of a crescendo action.
A further example of the prior art is that of U.S. Pat. No. 3,900,798 to Pomerantz et al. This patent describes a solid state alarm system which may be employed as a part of a clock radio. The system has capability of providing a crescendo of the alarm.
All of the prior art are considered to suffer from disadvantages because of sophistication and complication of circuitry, all resulting in an expensive consumer-type product in the marketplace. The present invention is directed to a rather simple circuit with far less complication and which results in a less expensive product. Further, the present device has a capability unique in the art of clock-radios whereby the radio volume after providing initial wake-up is caused to decrescendo as an alarm in the from of a strike and chime is caused to crescendo through a cross-fade out operation. Thus, the alarm provides the dominant sound until it shall be terminated, at which time the radio tone returns to the initial volume.